Steam-heated rotating cylinders are utilized in a number of industries for producing and processing various materials, such as paper. For example, a web of paper can be dried by passing it over one or more heated cylinders. In the corrugating industry, the cylinders are often less than two feet in diameter and can be ten to fifteen feet in length. Steam is introduced into the cylinder through a rotating seal, also known as a rotary joint. The steam inside the cylinder transfers its heat to a web of material that is disposed on the outside of the cylinder through the shell of the cylinder. As the heat is transferred from the hot steam to the web, the steam inside the cylinder condenses. The condensate thus formed is then removed from the cylinder through a syphon pipe that is connected to an external pipe or tank through the rotary joint.
At low rotational speeds, the residual condensate inside the cylinder will tend to accumulate in a puddle at the bottom of the cylinder, which is referred to as a “ponding” state. As the rotational speed of the cylinder increases, the condensate in the puddle will begin to rotate with the cylindrical shell but fall back into the puddle as it nears the top of the cylinder. This is referred to as a “cascading” state. At high rotational speeds, the condensate follows the cylinder around the entire inside periphery of the cylindrical shell in a state that is referred to as “rimming.”
When the cylinder is rotated, the water is rotated along with the cylinder itself, and the added weight of the water requires that an increased rotational force be applied to rotate the cylinder. In order to minimize the power required to rotate the cylinders in the ponding and cascading states, and to maximize the transfer of heat through the condensate in the rimming state, the syphon pipe is typically designed to minimize the amount of condensate that is disposed within the cylinder.
At high rotational speeds, the rimming layer of condensate is very stagnant and forms an insulating barrier between the steam inside the cylinder and the inside surface of the cylindrical shell of the cylinder. Even thin residual layers of condensate can provide significant resistance to the transfer of heat from the steam to the cylindrical shell.
It is known that generating turbulence in the rimming layer increases the rate of convective heat transfer through the condensate layer. Turbulence bars have been previously used for this purpose. Turbulence bars are disposed within the cylinder and are held against the inside surface of the cylindrical shell by various means. The turbulence bars generate turbulence in the rimming layer of the condensate that forms between the individual bars. This increase in condensate turbulence increases the rate of heat transfer and tends to improve the uniformity of heat transfer from the cylinder.
Various structures have been developed for fixing turbulence bars within the interior of the cylinder. These structures include magnets, springs, pins, and bolts. The bars are typically held to the inside surface of the cylindrical shell of the cylinder using a plurality of hoops or hoop segments that are pressed toward the inner surface of the cylindrical shell. For example, one prior art design uses a threaded turnbuckle with locking nuts that interconnects two hoop segments and can be adjusted to press the hoop segments outward. As another example, some prior art designs place springs between hoop segments to press the hoop segments outward.